Untitled

<?php
include "Header.php";

$Configuration = mysqli_fetch_object($Configuration = mysqli_query($connection, "SELECT * FROM Configuration"));

if ($Configuration->Register == "true") {
    if (!$User) {
        echo '
<!DOCTYPE html>
<html>
<body>
   <p style="text-align: center;">&nbsp;</p>
   <table style="width: 454px; margin-left: auto; margin-right: auto;">
       <tbody>
           <tr>
               <td style="width: 311px;">
                   <div id="LargeText" style="text-align: center;">
                       <strong>Register</strong>
                   </div>
                   <form action="register.php" method="post">
                       <table cellpadding="0" cellspacing="5" style="width: 341.5px; margin-left: auto; margin-right: auto;">
                           <tbody>
                               <tr>
                                   <td style="padding-right: 1px; width: 149px;"><strong>Username</strong></td>
                                   <td style="width: 190.5px;"><input name="user" type="text"></td>
                               </tr>
                               <tr>
                                   <td style="padding-right: 5px; width: 149px;"><strong>Password</strong></td>
                                   <td style="width: 190.5px;"><input name="pass" type="password"></td>
                               </tr>
                               <tr>
                                   <td style="padding-right: 5px; width: 149px;"><strong>Confirm Password</strong></td>
                                   <td style="width: 190.5px;"><input name="confirmpass" type="password"></td>
                               </tr>
                               <tr>
                                   <td style="padding-right: 5px; width: 149px;"><strong>Email</strong></td>
                                   <td style="width: 190.5px;"><input name="email" type="text"></td>
                               </tr>
                           </tbody>
                       </table>
                       <p style="text-align: center;"><input type="submit" name="submit" value="Register"></p>
                   </form>
               </td>
           </tr>
       </tbody>
   </table>
</body>
</html>
';
        $Username        = mysqli_real_escape_string($connection, $_POST['user']);
        $Password        = mysqli_real_escape_string($connection, $_POST['pass']);
        $ConfirmPassword = mysqli_real_escape_string($connection, $_POST['confirmpass']);
        $Email           = mysqli_real_escape_string($connection, $_POST['email']);
        $Submit          = mysqli_real_escape_string($connection, $_POST['submit']);
        $ref             = mysqli_real_escape_string($connection, $_GET['ref']);

        function is_alphanumeric($username) {
            return (bool) preg_match("/^([a-zA-Z0-9])+$/i", $username);
        }

        if ($Submit) {
            die("sssdfsofskllsflj");
            $Username = filter($Username);
            $ref      = filter($_GET['ref']);
            if (!$Username || !$Password || !$ConfirmPassword || !$Email || !$ReCaptcha) {
                echo"sdfsfdosdf";
                echo "<head><center><div id='Error'>Please fill in all of the fields.</div></center></head>";
            } else {
                echo"2129";
                $userExist  = mysqli_query($connection, "SELECT * FROM Users WHERE Username='$Username'");
                $userExist  = mysqli_num_rows($userExist);
                $userExist1 = mysqli_query($connection, "SELECT * FROM Users WHERE OriginalName='$Username'");
                $userExist1 = mysqli_num_rows($userExist1);
                if ($userExist > 0) {
                    echo "<div id='Error'>That username already exists.</div>";
                } elseif ($userExist1 > 0) {
                    echo "<div id='Error'>That username already exists.</div>";
                } else {
                    if ($ConfirmPassword != $Password) {
                        echo "<div id='Error'>Your password and confirm password does not match.</div>";
                    } else {
                        if (strlen($Username) >= 15) {
                            echo "<div id='Error'>Your username is above fifteen (15) characters!</div>";
                        } elseif (strlen($Username) < 1) {
                            echo "<div id='Error'>Your username is under one (1) character!</div>";
                        } elseif (!is_alphanumeric($Username)) {
                            echo "<div id='Error'>Only A-Z and 1-9 is allowed, or there is profanity in your username.</div>";
                        } else {
                            if ($ref) {
                                $getRef   = mysqli_query($connection, "SELECT * FROM Users WHERE ID='$ref'");
                                $gR       = mysqli_fetch_object($getRef);
                                $RefExist = mysqli_num_rows($getRef);
                                if ($RefExist == 0) {
                                } else {
                                    $userExist = mysqli_query($connection, "SELECT * FROM Users WHERE Username='$Username'");
                                    $userExist = mysqli_fetch_object($userExist);
                                    mysqli_query($connection, "UPDATE Users SET SuccessReferrer=SuccessReferrer + 1 WHERE ID='$ref'");
                                    mysqli_query($connection, "INSERT INTO Referrals (ReferredID, UserID) VALUES('$ref','$userExist->ID')");
                                }
                            }

                            $_ENCRYPT = password_hash($Password, PASSWORD_DEFAULT);
                            $IP       = $_SERVER['REMOTE_ADDR'];
                            mysqli_query($connection, "INSERT INTO Users (Username, Password, Email, IP) VALUES('$Username','$_ENCRYPT','$Email','$IP')");
                            $_SESSION['Username'] = $Username;
                            $_SESSION['Password'] = $_ENCRYPT;
                            header("Location: index.php");
                        }
                    }
                }
            }
        }
    }
}